Electrical contacts are conventionally provided as a means to provide separable continuity between the electrically conductive core of an insulated electrical wire and an electrical terminal, conductive core of another insulated electrical wire, or other device. They are used, for example, in lieu of solder joints for providing an electrical connection. The electrically conductive cores are typically composed of a conductive metallic material such as, copper, silver, gold, aluminum, their alloys, or the like. The cores may or may not be plated with a conductive-metal plating material.
Electrical contact assemblies often take a form in which a male or female mating portion and a barrel portion are generally aligned along a common axis. The contact is generally designed as either a male pin configured to be axially inserted into a female socket, or a female socket into which a male pin is to be inserted. In either configuration, the purpose of mating the male pin and the female socket is to complete an electrical circuit. The barrel portion or barrel has an axially extending tubular bore that is configured to receive and provide an attachment location for the core of an insulated electrical wire. When the barrel is of the type described as a closed barrel, the electrical contact is typically gold plated. For a plated contact, a small hole is radially disposed through the tubular wall of the barrel near the bottom end of the closed axially extending bore. This hole is required to allow full surface contact with plating solutions during the plating or manufacturing process.
During the assembly of the electrical contact to the end of an electrical wire, the insulation is stripped from the tip of the wire to expose a short length of the electrically conductive core of the wire. The short length of exposed core is then inserted into the axially extending bore in the tubular barrel of the electrical contact. The core of the wire may be either stranded or solid. The tubular wall of the barrel is then typically crimped into contact and electrical continuity with the bare tip of the core of the wire that is within the axial cavity. In some connector assemblies, the tubular barrel is also deformed, typically by crimping, into a hermetically sealing contact with the insulated coating on the wire.
As mentioned above, a hole, sometimes referred to as a bleeder hole, is disposed through the tubular wall of the barrel to facilitate plating. Consequently, the tubular bore of the closed barrel and the exposed core of the wire are partially exposed to the environment as a result of the hole. This hole produces an undesirable pathway for environmental contaminants, such as water or corrosive chemicals, to propagate to the conductive core of the wire. Entry of such contaminants can corrode the wire core, increase the electrical resistance value of the core/barrel interface, embrittle the core, or otherwise degrade the quality or longevity of the electrical and physical properties of the contact assembly.
Previous attempts to environmentally seal the bleeder hole have proven to be costly or have resulted in degradation of the core/bore interface. One ineffective solution involved placing a silver or malleable sleeve between the electrically conductive core of the wire and the bore of the barrel. Such a solution is costly due to the silver and only provided a moderate performance in environmentally sealing the contact assembly. Also, with such an arrangement, electrical conductivity between the core and the bore of the barrel was diminished and the contact resistance increased. Additionally, tensile strength of the mated wire and contact was diminished by the addition of the silver sleeve.
Another ineffective solution required placing a sleeve over the barrel of the contact assembly. While this avoided degrading the electrical connection of the core to the bore of the barrel, the loose outer sleeves could be lost or separated from the connector assembly prior to crimping them in place. Additionally, the loose outer sleeves often required complex geometries to ensure an adequate seal when applied with relatively complex crimping profiles.
Therefore, there is a need for an effective environmentally sealed contact that yields excellent electrical conductivity as well as a robust physical design while being generally free of loose parts or sealing sleeves.